'\" t
.\"     Title: pam_filter
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 11/22/2024
.\"    Manual: Linux-PAM Manual
.\"    Source: Linux-PAM
.\"  Language: English
.\"
.TH "PAM_FILTER" "8" "11/22/2024" "Linux\-PAM" "Linux\-PAM Manual"
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.nh
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.SH "NAME"
pam_filter \- PAM filter module
.SH "SYNOPSIS"
.HP \w'\fBpam_filter\&.so\fR\ 'u
\fBpam_filter\&.so\fR [debug] [new_term] [non_term] run1|run2 \fIfilter\fR [\fI\&.\&.\&.\fR]
.SH "DESCRIPTION"
.PP
This module is intended to be a platform for providing access to all of the input/output that passes between the user and the application\&. It is only suitable for tty\-based and (stdin/stdout) applications\&.
.PP
To function this module requires
\fIfilters\fR
to be installed on the system\&. The single filter provided with the module simply transposes upper and lower case letters in the input and output streams\&. (This can be very annoying and is not kind to termcap based editors)\&.
.PP
Each component of the module has the potential to invoke the desired filter\&. The filter is always
\fBexecv\fR(2)
with the privilege of the calling application and
\fInot\fR
that of the user\&. For this reason it cannot usually be killed by the user without closing their session\&.
.SH "OPTIONS"
.PP
.PP
debug
.RS 4
Print debug information\&.
.RE
.PP
new_term
.RS 4
The default action of the filter is to set the
\fIPAM_TTY\fR
item to indicate the terminal that the user is using to connect to the application\&. This argument indicates that the filter should set
\fIPAM_TTY\fR
to the filtered pseudo\-terminal\&.
.RE
.PP
non_term
.RS 4
don\*(Aqt try to set the
\fIPAM_TTY\fR
item\&.
.RE
.PP
runX
.RS 4
In order that the module can invoke a filter it should know when to invoke it\&. This argument is required to tell the filter when to do this\&.
.sp
Permitted values for
\fIX\fR
are
\fI1\fR
and
\fI2\fR\&. These indicate the precise time that the filter is to be run\&. To understand this concept it will be useful to have read the
\fBpam\fR(3)
manual page\&. Basically, for each management group there are up to two ways of calling the module\*(Aqs functions\&. In the case of the
\fIauthentication\fR
and
\fIsession\fR
components there are actually two separate functions\&. For the case of authentication, these functions are
\fBpam_authenticate\fR(3)
and
\fBpam_setcred\fR(3), here
\fBrun1\fR
means run the filter from the
\fBpam_authenticate\fR
function and
\fBrun2\fR
means run the filter from
\fBpam_setcred\fR\&. In the case of the session modules,
\fIrun1\fR
implies that the filter is invoked at the
\fBpam_open_session\fR(3)
stage, and
\fIrun2\fR
for
\fBpam_close_session\fR(3)\&.
.sp
For the case of the account component\&. Either
\fIrun1\fR
or
\fIrun2\fR
may be used\&.
.sp
For the case of the password component,
\fIrun1\fR
is used to indicate that the filter is run on the first occasion of
\fBpam_chauthtok\fR(3)
(the
\fIPAM_PRELIM_CHECK\fR
phase) and
\fIrun2\fR
is used to indicate that the filter is run on the second occasion (the
\fIPAM_UPDATE_AUTHTOK\fR
phase)\&.
.RE
.PP
filter
.RS 4
The full pathname of the filter to be run and any command line arguments that the filter might expect\&.
.RE
.SH "MODULE TYPES PROVIDED"
.PP
All module types (\fBauth\fR,
\fBaccount\fR,
\fBpassword\fR
and
\fBsession\fR) are provided\&.
.SH "RETURN VALUES"
.PP
.PP
PAM_SUCCESS
.RS 4
The new filter was set successfully\&.
.RE
.PP
PAM_ABORT
.RS 4
Critical error, immediate abort\&.
.RE
.SH "EXAMPLES"
.PP
Add the following line to
/etc/pam\&.d/login
to see how to configure login to transpose upper and lower case letters once the user has logged in:
.sp
.if n \{\
.RS 4
.\}
.nf
        session required pam_filter\&.so run1 /lib/security/pam_filter/upperLOWER
      
.fi
.if n \{\
.RE
.\}
.sp
.SH "SEE ALSO"
.PP
\fBpam.conf\fR(5),
\fBpam.d\fR(5),
\fBpam\fR(8)
.SH "AUTHOR"
.PP
pam_filter was written by Andrew G\&. Morgan <morgan@kernel\&.org>\&.
